Cobalt 60 gamma-irradiation has become an accepted sterilization technique for medical devices. A dose rate of 2.5 Mrads is customary, although dosages as high as 5.5 Mrads may be used. For shaped polymeric articles such as syringes, tubing, tissue culture flasks, packaging film, etc., degradation during or subsequent to irradiation results in problems such as embrittlement, discoloration and reduced heat and light stability.
U.S. Pat. Nos. 4,110,185, 4,274,932 and 4,467,065 disclose stabilization of polymers against embrittlement during or subsequent to irradiation by incorporating a mobilizer such as a hydrocarbon oil, halogenated hydrocarbon oil, phthalic ester oil, vegetable oil, or silicone oil.
European patent application 78,603 discloses the use of a hindered amine or its salt, N-oxide, N-hydroxide or N-nitroxide to stabilize polyolefin medical articles, e.g., syringes, against yellowing and/or embrittlement resulting from radiation sterilization.
British Patent 1,050,802 discloses the use of a stabilizer system comprising an organic carboxylic acid, e.g., adipic or benzoic acid, and an organic phosphite for articles such as disposable syringes made from radiation sterilizable polyolefin compositions.
U.S. Pat. No. 4,460,445 discloses an olefinic polymer composition containing a hindered phenolic stabilizer and a benzaldehyde acetal which is resistant to degradation when subjected to sterilizing amounts of radiation.
It is known to use polypropylene fibers for medical applications such as gauze, bottle stuffing, a component of nonwoven products such as surgical gowns and operating room barriers, and in combination with other fibers in fabrics. These products, packaged in plastic films, paper envelopes or glass vials, have been sterilized by irradiation, a method which is both economical and convenient. However, a major obstacle to commercial acceptance of these fibrous products is the disagreeable odor generated upon irradiation. Odor may also be a problem in polypropylene shaped articles other than fibers, e.g. molded articles, film for packaging, etc. None of the prior art stabilizer systems addresses the problem of odor generation.